1. Field of Invention
The invention relates to a centerdrilling machine for rod material comprising a machine bed, two center drilling units, of which one is fixed and the other is adapted to be moved relative thereto. More specifically, the drilling units each comprise a centering cone, adjustable shifting workpiece rests, and a coolant supply system. The movable drilling unit is adapted fro shifting movement by hydropneumatic means operated automatically or manually and in conjunction with the stationary drilling unit.
2. Description of the Prior Art
Center drilling machines having substantial advantages as compared with conventional lathes with center drilling devices are known in the art. In the case of lathes with center drilling devices the conventional arrangement utilizes a drilling tool, mounted in a shifting manner on the lathe bed. The drill may be pressed against the center of the workpiece by a simple lever mechanism to drill the hole into the workpiece. The workpiece itself is held in one of two holding devices of the lathe. In order to carry out center drilling at both ends, the workpiece must be removed from the chuck after the first hole has been drilled, turned around and then firmly mounted again in order to be able to make the second drilled hole in the same fashion as the first operation.
The time consuming nature of center drilling at both ends of a workpiece in a conventional lathe and the substantial expenditure of skill and precision required for the manual labor involved leave a great deal to be desired from the standpoint of economy and efficiency.
Center drilling machines have also been proposed, which carry out center drilling at the two ends simultaneously, the workpiece being positioned in holding chucks. The clamping of the workpiece into the correct position in the chucks require a substantial amount of time and, with every change in the diameter of the workpiece, the holding chucks must be set precisely to ensure that the centering drill is exactly positioned on the center point of the workpiece. Thus, while the drilling may be performed in a single step, a substantial time requirement for any retooling must be permitted. The retooling time is required for any changes of the workpiece lengths, diameters, shapes, etc. Therefore, such center drilling machines are only feasible from an economic standpoint in the case of large scale mass production.
In another type of conventional centering machines, the work material is placed loosely on the workpiece rest, and is centered by sliding in centering cones of spring mounted centering sleeves on shifting of the center drilling units, the centering cones being so slotted that the side adjacent to the workpiece consists of three jaws offset by 120.degree.. The depth of drilling is set by turning a setting nut, which is locked by a lock nut. As a result, clamping of the workpiece is not necessary and there is furthermore, the possibility of drilling the centering holes at the two ends with a precise distance setting. With this center drilling machine, it is possible to easily provide rods of different diameters with center holes. If, however, the length of the rods is changed, substantial time is required for retooling. Usually, retooling will involve at least the removal of a base plate, on which the advance slide of the adjustable center drilling unit is arranged, for coarse adjustment, to shift it and then lock it into position again, following which fine setting and final fixing in position can be carried out. Furthermore, adjustment in the depth of drilling, which must be carried out on both center drilling units manually, is time-consuming and involves the danger of inaccurate adjustment of the setting nuts to different lengths or careless tightening of the lock nuts. As a result, this center drilling machine is also only suitable for large scale mass production runs.
Accordingly, it is an object of the present invention to provide an improved center drilling machine in such a manner that it is possible to center rod materials of differing lengths, differing cross-sections and differing diameters with only very short retooling times.
It is another object of the present invention to drill center holes with various different depths as may be required.
It is yet a further object of the present invention to make possible the automation of center drilling operations. and to carry them out rapidly.
In a preferred embodiment, the center drilling machine of the present invention may be used for jobbing and may also be capable of carrying out final machining after carrying out a simple modification making it reasonable and advantageous to use the machine also in small factories and workshops, where no possibility of mass production exists.
Further objects and advantages of the present invention will become apparent from the brief summary of the invention which follows and the more detailed description of the preferred embodiments and drawings relative thereto.